The fitting of the present invention is generally related to those types of fittings disclosed in U.S. Pat. Nos. 3,738,688; 3,779,587; 3,868,132; 4,154,465; and 4,225,159.
The fittings disclosed in the above-mentioned U.S. patents are generally of two types. The first type grasps the tube by means of a collet around the outside of the smooth wall tube and compresses a tubular plug against the outer diameter of the tube upon translation of a ram element within the housing thereof. This type of fitting provides a good seal and holding action so that fluids passing through the smooth wall tube may be sealed by the fitting, or may be conveyed out of the fitting into auxiliary tubing mounted thereto. The second type of fitting is mounted to the ends of the tube by compressing a plug against the inner diameter of the tube upon translation of a ram element while a collet grasps a outer diameter of the tube. These types of fittings are especially useful on thin walled tubing wherein the gripping force of the collet is counter-balanced by the sealing of the plug. Both types of fittings utilize a manually operated torque transmitting lever to translate a ram element which seals and holds the smooth wall tube.
The present invention provides a fitting that grips on the outside diameter and also seals on the inside diameter. The gripping on the outside diameter is accomplished by the operation of a piston forced into operation by a fluid, the piston forcing a collet operator to cause a split collet to grasp the outside diameter of the tube. The fluid is under pressure and flows through the fitting to the smooth wall tube which is connected to the device to be tested. A fluid pressure further causes the seal on the inside diameter of the tube to compress around an elongated seal screw having a passage which allows the fluid to flow through the fitting. Initial gripping and sealing of the tube into the fitting is accomplished by a mechanical spring.
A fitting is applicable for use on a wide range of tube sizes, but has generally been found most applicable to tube ends with a minimum inside diameter of 0.295 inches. The fitting's configuration is designed for use on condensor and evaporator cores or other high pressure cores which periodically should be tested.
Accordingly, it is an object of the present invention to provide improved fittings for mounting to the ends of smooth wall tubes.
More particularly, it is an object to provide such a fitting which is semi-automatic and does not require manual operation of a lever or other handle-type torque transmitting device to accomplish the installation of the fitting.
It is an additional object to provide a fitting which is operable by fluid means while having the initial gripping and sealing accomplished by spring-loaded mechanical pressure.